Microsoft TCP/IP Host Name Resolution Order

Summary

This article discusses the different methods of host name to IP address resolutions used by Microsoft Windows clients. The sequence of methods is different than the sequence used to resolve NetBIOS names to IP addresses.

More Information

On a network using the TCP/IP protocol, it is necessary to convert names of resources to IP addresses to connect to these resources. Microsoft Windows clients will follow a sequence of methods in attempting to resolve a name to an address, stopping the search when it successfully matches a name to an IP address.

There are two main sequences used in almost all cases: NetBIOS resolution and Host name resolution. Clients connecting to resources on Microsoft servers, typically through Windows File Manager or Network Neighborhood, most often use NetBIOS name resolution.

For additional information, please see the following article in the Microsoft Knowledge Base:

119493 NetBIOS over TCP/IP Name Resolution and WINS

Host name resolution resolves the names of TCP/IP resources that do not connect through the NetBIOS interface. The most common example of this is a Web browser such as Microsoft Internet Explorer. Other examples include Internet applications such as Ping, FTP, and Telnet. Many modern database and mail applications that connect using Winsock, the Microsoft Windows implementation of TCP/IP sockets, also use host name resolution. Examples of these types of applications are Outlook and Exchange.

When troubleshooting name resolution issues, it is important to narrow down whether the application is resolving a NetBIOS name or a host name.

NOTE: In the context of this article, the term «client» does not necessarily refer to a workstation. A Windows NT server will take the role of client when it requires access to resources that require host name resolution.

Host name resolution generally uses the following sequence:

The client checks to see if the name queried is its own.

The client then searches a local Hosts file, a list of IP address and names stored on the local computer.

NOTE: The Hosts file location depends on the operating system:

Windows NT %Systemroot%\System32\Drivers\Etc
Windows 95 \
Windows for Workgroups \
Windows 3.1 \
MS-Client 3.0 \Net
Lan Manager 2.2c Client \Net
Where %Systemroot% is the folder in which Windows NT is installed, is the drive on which the OS is installed, and refers to a boot floppy disk or drive C.

A sample hosts file, Hosts.sam, is installed with the TCP/IP protocol showing the proper format.

Domain Name System (DNS) servers are queried.

If the name is still not resolved, NetBIOS name resolution sequence is used as a backup. This order can be changed by configuring the NetBIOS node type of the client.

The Windows client will try each of these methods until it either successfully resolves the name or exhausts these methods. Windows NT, Windows 95, and Windows for Workgroups clients using Microsoft TCP/IP 3.11b follow this sequence. Lan Manager 2.2c or Microsoft Client 3.0 clients will not use NetBIOS name resolution as a backup.

For additional information, please see the following articles in the Microsoft Knowledge Base:

169141 NetBIOS and hostname resolution for MS-Client and LM 2.2c
When resolving names the client will skip methods for which it is not configured. For example, if there is no hosts file on the system, then it will skip step #2 above and try a query to a DNS server. If no DNS server IP addresses are entered in the client TCP/IP configuration, then the client will skip to the next step in the sequence after DNS.

The method for changing host name resolution order differs among operating systems and versions. These are documented in the Resource Kits for the specific operating systems, as well as in the Microsoft Knowledge Base.

For additional information, please see the following articles in the Microsoft Knowledge Base:

171567 Windows NT 4.0 ServiceProvider Priority Values Not Applied

139270 How to Change Name Resolution Order on Windows 95 and Windows NT

119372 Setting the Name Resolution Search Order for TCP/IP-32

Troubleshooting

Problem: Client is unable to resolve a host name.

If a client cannot resolve a host name, then it is best to verify the Host name resolution sequence listed above that the client should be using. If the name does not exist in any of the resources that the client uses, then you must decide to which resource to add it. If the name exists in one of the resources, such as a DNS server or a Windows Internet Name Service (WINS) server and the client is not resolving the name correctly, focus your attention on troubleshooting that specific resource.

Also, confirm that the client is trying to resolve a host name and not a NetBIOS name. Many applications have multiple methods that they can utilize to resolve names, this is especially true of mail and database applications. The application may be configured to connect to resources using NetBIOS. Depending on the client configuration the client may bypass host name resolution. From there it will be necessary to either change the connection type to TCP/IP sockets or to troubleshoot the problem as a NetBIOS issue.

Problem: Client resolves a name very slowly, or fails to resolve a name and takes a long time to report a failure.

Having DNS servers configured in a client’s TCP/IP configuration, but the server is not available to the client usually causes this. Because the TCP/IP protocol assumes an unreliable network, a client will repeatedly attempt to connect to a DNS server before abandoning the attempted query. The client will then attempt to query a second DNS server if one is configured and take the same time to fail. Only then will the client step through to NetBIOS name resolution as described above.

There are three ways to approach this issue.

If the host name is correctly entered in a host file, it will be resolved before the client attempts to query DNS. This solution works well if DNS servers are temporarily unreachable and there is a small number of host names that need to be resolved . Manually configuring Hosts files for numerous clients may be prohibitive. -or-

If DNS servers are available, but the DNS Server addresses in the clients TCP/IP configuration are incorrect, then correcting these addresses will allow the clients to contact the DNS servers immediately. Even if a DNS server reports that it cannot resolve a name, this will happen much faster than if the client cannot reach a DNS server at all. -or-

If DNS servers are configured on the client, but these servers are permanently unavailable, then remove the IP addresses of the DNS servers from the client configuration. The client will then bypass the DNS lookup without delay. -or-

If records in the DNS database are missing or incorrect, then there will be a delay as DNS servers query other DNS servers before reporting that they cannot resolve the name. This will usually cause a delay of just a few seconds.

For additional information on TCP/IP and name resolution, please see the following white paper available on the Microsoft anonymous ftp server:

Release and Renew Your IP Address in Microsoft Windows

Use the IPconfig command to fix common networking errors

Releasing and renewing the IP address on a computer running the Windows operating system resets the underlying IP connection, which often eliminates common IP-related issues, at least temporarily. It works in a few steps to disengage the network connection and refresh the IP address.

Instructions in this article apply to Windows 10, Windows 8.1, Windows 8, and Windows 7.

Windows: Release and Renew IP Addresses

Under normal conditions, a device can use the same IP address indefinitely. Networks usually reassign correct addresses to devices when they first join. However, technical glitches with DHCP and network hardware can lead to IP conflicts and other problems that prevent the networking system from working correctly.

When to Release and Renew the IP Address

Scenarios in which releasing the IP address and then renewing it might be beneficial include:

• When connecting a computer directly to a modem.
• When physically moving a computer from one network to another such as from an office network to home or from home to a hotspot.
• When experiencing an unexpected network outage.

Release and Renew an IP Address With Command Prompt

Here’s how to release and renew the address of any computer running the Windows operating system.

Open Command Prompt. The quickest method is to press Win+R to open the Run box dialog, enter cmd, then press Enter.

Enter ipconfig /release and press Enter.

In the command results, the IP address line shows 0.0.0.0 as the IP address. This is normal because the command releases the IP address from the network adapter. During this time, your computer has no IP address and cannot access the internet.

Enter ipconfig /renew and press Enter to get a new address.

When the command is finished, a new line appears at the bottom of the Command Prompt screen that contains an IP address.

More Information About IP Release and Renew

Windows may receive the same IP address after renewal as it had before. This phenomenon is normal. The desired effect of deleting the old connection and starting a new one occurs independently of which address numbers are involved.

Attempts to renew the IP address may fail. One possible error message may read:

• An error occurred while renewing interface [interface name] : unable to contact your DHCP server. Request has timed out.

This particular error indicates that the DHCP server may be malfunctioning or is unreachable. Reboot the client device or the server before proceeding.

Windows also provide a troubleshooting section in Network and Sharing Center and Network Connections that run diagnostics that include an equivalent IP renewal procedure if it detects that it’s needed.

3 Ways to Resolve IP address Conflict on windows 10

Windows PC or Laptop showing popup error message Windows has detected an IP address conflict and due to this windows fails to connect network & Internet? When two computers should have the same IP address on the same network, they won’t be able to access the Internet and they will face the above error. As having the same IP address on the same network creates a conflict. That’s why windows result IP address conflict Error message. If you are also having the same problem continue Reading We have complete solutions to resolve IP address conflict on windows based PC.

Issue: Windows has detected an IP address conflict

Another computer on this network has the same IP address as this computer. Contact your network administrator for help resolving this issue. More details are available in the Windows System event log.

Why IP address conflict Occur?

This IP address conflict error mostly occurs on local Area networks. As we create local area connection to share resources file, folder, printer on different computers. Local networks are created in two ways by assigning a static IP to each computer and by configuring a DHCP server to assign a dynamic IP addresses to each computer within a specific range. Some time two computers have same IP address on a network. Therefore, the two computers can not communicate within the network and an error message occurs saying there is an IP address conflict on the network.

Resolve IP Address Conflict On Windows PC

Restart Router: Start with Basic simply Restart your Router, Switch ( if connected ) And your Windows PC. If any Temporary Glitch Causing the issue reboot/power cycle the device clear the issue, And you will back to the normal working stage.

Disable/Re-enable Network Adapter: Again this is another most effective solution to fix most of network/Internet related problems. To do this press Windows + R, type ncpa.cpl hit enter. Then right-click on your Active network adapter select Disable. Now Restart your computer, After that Again open the Network and internet connection window using ncpa.cpl command. This time right-click on the network adapter ( which you disabled previously ) then select Enable. After that check, your connection may be back to normal stage.

Configure DHCP for Windows

This is the most effective solution I personally found to resolve IP address conflict on windows computers. This is very simple if you are using a static IP Address ( manually configured ) Then change it, configure DHCP to obtain IP Address Automatically which mostly most the problem. You Can configure DHCP to obtain IP address Automatically by following the steps below.

First press Windows + R, Type ncpa.cpl and hit enter key to open the Network connections window. Here right-click on your Active network Adapter and select properties. Select Internet Protocol Version 4(TCP/IPv4) and click Properties. A new popup window open, Here Select the radio button Obtain IP address automatically. and Select Obtain DNS server address automatically As shown image below. Click OK to close the TCP/IP Properties window, the Local Area Connection Properties window, and Restart your computer.

Flush DNS and Reset TCP/IP

This is another Effective Solution if you have already Configured DHCP for Obtain IP Address Automatically And getting IP conflict error message then flush the DNS cache, And Reset the TCP/IP will renew a new IP address from DHCP server. Which most probably fix the issue on your System.

To flush DNS cache and Reset TCP/IP first you need to open the command prompt as administrator. Then perform Command Below one by and press enter to execute the same.

• netsh int ip reset
• Ipconfig /release
• Ipconfig /flushdns
• Ipconfig /renew

After performing These commands type exit to close the command prompt, And restart your windows computer to take effect the changes. Now on next start check, There is no more IP Address conflict error message on your PC.

Disable IPv6

Again Some users report Disable IPV6 help them to resolve this IP Address conflict error message. You can do this by following below.

• Press Windows + R, type ncpa.cpl, and press enter key.
• On the network, connections window right-click on active network adapter select properties.
• on the new popup window uncheck IPv6 as shown image below.
• click ok to apply and close the current window and check the problem resolved.

These are some most effective solutions to Resolve IP address conflict on windows PC. I sure apply these solutions fix the issue “Windows has detected an IP address conflict” and your Network & Internet connection Start working normally. Still, need any help about this IP Address conflict problem feel free to discuss in the comments below.